Fix shl folding in DAG combiner.

[chfast]

Summary

The code responsible for shl folding in the DAGCombiner was assuming incorrectly that all constants are less than 64 bits. This patch simply changes the way values are compared.

[andreadb]

Hi Pawel,

The change looks good to me.
You can simplify the test case (see comment below).

Thanks,
Andrea

test/CodeGen/X86/fold-vector-shl-crash.ll

4–8 ↗

(On Diff #28109)

if you define @test as a function returning a <2 x i256> vector value, then you can get rid of basic block 'Loop' and simply return %B.
Basically, the loop is not needed to reproduce the crash in the dag combiner.

[chfast]

• Simplify the regression test.

llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

SDValue DAGCombiner::visitSHL(SDNode *N) {
   // fold (shl c1, c2) -> c1<<c2
   ConstantSDNode *N0C = getAsNonOpaqueConstant(N0);
   if (N0C && N1C && !N1C->isOpaque())
     return DAG.FoldConstantArithmetic(ISD::SHL, SDLoc(N), VT, N0C, N1C);
   // fold (shl 0, x) -> 0
   if (isNullConstant(N0))
     return N0;
   // fold (shl x, c >= size(x)) -> undef
-  if (N1C && N1C->getZExtValue() >= OpSizeInBits)
+  if (N1C && N1C->getAPIntValue().uge(OpSizeInBits))
     return DAG.getUNDEF(VT);
   // fold (shl x, 0) -> x
   if (N1C && N1C->isNullValue())
     return N0;
   // fold (shl undef, x) -> 0
   if (N0.getOpcode() == ISD::UNDEF)
     return DAG.getConstant(0, SDLoc(N), VT);
   // if (shl x, c) is known to be zero, return 0

llvm/trunk/test/CodeGen/X86/fold-vector-shl-crash.ll

+; RUN: llc < %s | FileCheck %s
+
+;CHECK-LABEL: test
+define <2 x i256> @test() {
+  %S = shufflevector <2 x i256> zeroinitializer, <2 x i256> <i256 -1, i256 -1>, <2 x i32> <i32 0, i32 2>
+  %B = shl <2 x i256> %S, <i256 -1, i256 -1> ; DAG Combiner crashes here
+  ret <2 x i256> %B
+}